ALL the signs are that a brutal and totally unnecessary trans-Atlantic drama war is going to break out unless the American stage union Actors Equity relaxes its rules against imported players.

The Post’s Michael Riedel reported the other day that Actors Equity has rejected a bid to bring the British cast of the acclaimed ”Oklahoma!” revival to Broadway in the fall, with a view to replacing it with a local cast within three months.

Since that decision, my London sources report that the British theater establishment – both the unions and the producers – has had it up to here with the American union.

And even our Irish cousins are making threats. Sinead Cusack, the renowned Cork actress, is fuliminating against ”discrimination” on Broadway. Sinead complains that it’s OK for ”starlets” like Nicole Kidman to play London’s West End, but Irish and British actors have the devil of a time getting on the American stage.

”Our own actors should be given equal opportunity,” Cusack says. ”It’s all very well for those Americans being the cream in our coffee, but we don’t want it all to turn to sour milk.”